Why did you say that training everything twice a week is bad? All I have been reading lately is how bad it is to train each muscle only once every week. Apparently high frequncy is good and all the stadard Mon-Wed-Fri, Chest/Tris, /Back/Bis/, Legs/Shoudlers routines are garbage. At least thats what I have been reading lately. I'm looking to start a higher frequency routine also.
You may possibly be able to work up to that volume eventually, but you have to ease your way into it. You can't just jump from a more traditional split to lifting 6 days per week at a high level of volume. That's kind of nuts in my opinion.
I like P's first idea of training the different performance related fitness attributes each session. That should help prevent general adaptation syndrome and overtraining in the long run.
The only time it's bad to feel the burn is when you're peeing...
You don't address one important question. What happens after the Sunday workout? Do you take Monday off, making this effectively a 3 on, 1 off routine, or do you start the same cycle over again so that by Wednesday, you've worked out 6 days straight?